Transcript Ohio_2007_tiemann.ppt

Leibniz Universität
Hannover
Spectroscopy of atom pairs and cold collisions
Eberhard Tiemann, Horst Knöckel
(Gottfried Wilhelm Leibniz Universität Hannover)
Asen Pashov
(University Sofia)
Olga Docenko, Maris Tamanis und Ruvin Ferber
(University Riga)
Potential scheme of alkali dimers
example NaRb (Korek et al 2000)
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Na fine structure
Rb fine structure
entrance channel
high resolution Fourier spectroscopy
spectroscopy entrance
Spectroscopy of cold collisions
The spectroscopic workhorse
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mixing
B1
mixing
3 
c
Laser excitation
2
2
3 S+5 P
LIF
a
3

32S+52S
X1
high resolution Fourier spectroscopy
entrance channel
Example NaRb
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1
1
+
B  - X  system
0.10
0.08
Intensity
x30
0.06
0.04
1
3
+
3
3
+
[B  , c  , b  ] - a  system
0.02
0.00
10000
11000
12000
-1
Frequency [cm ]
13000
14000
Overlap of X1+ and a3+
X
a
2.5
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asymptote fNa=1 + fRb=2
2.0
intensity
1.5
1.0
0.5
0.0
-12
N = 19
-10
-8
-6
-4
-1
energy (cm )
-2
0
shape resonance
compare spacing  exchange energy
Diagram of Evaluation
Feshbach resonances
from cold collisions
data of X-state
data of a-state
single channel
potential fit
single channel
potential fit
coupled channel calculation
with atomic hyperfine parameters
corrections from
channel coupling
Convergence to coupled system of
3 +
1 +
X  and a 
prediction of cold collision properties:
Feshbach resonances, scattering lengths
also for isotopomers
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common asymptote
Spectroscopic results of molecule AB
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Ground states
Description of hyperfine interaction
Asymptotic atomic values are sufficient!
Fermi contact interaction
Potentials for X1+ and a3+ and their long range behavior
analytic form

 
H  aFAs A  iA
 
 aFB sB  iB
 correlations between Ci
exchange energy
molecular potentials from short range to almost 
prediction of cold collisions? !
Excited states
Hyperfine structure not or only poorly seen!
Potentials represented by spline interpolation: shelf structure or double well possible
Transition moments from ab initio calculations
probably sufficiently good
Spectroscopy of cold collisions
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Hannover
Molecular entrance channel  transfer to atom pair continuum
preparation of quantum state
energy resolution by laser width
Example Na2
Samuelis et al, PRA 63, 012710 (2000)
Atom pair entrance channel  integration over energy distribution
of cold ensemble
tuning the embedded bound state structure
 Feshbach resonances
Combination of molecular and Feshbach resonance
spectroscopy
example
40K 87Rb
Feshbach spectroscopy
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ensembles of Fermi and Bose atomic particles
and
Fermi molecular particles
by LENS 2005, JILA 2006, Hamburg 2006, Hannover 2007
Analysis with asymptotic potential branches
Derived quantities scattering lengths of “pure” singlet and triplet state
Molecular spectroscopy on 39K 85Rb and 39K 87Rb
Construction of “full” potentials
Hannover, Sofia, Riga 2006
Born-Oppenheimer approximation
probably
Describing the complete data set
Mass scaling of collision properties to other isotopes?
reliable ?
Continue with high precision experiments
Photoassociation
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Rb2
Heinzen et al, Bloch et al
singlet/triplet
n2
n1
Na2
Lett et al
K2
Stwalley et al
KRb Stwalley et al
pure triplet
“pure” singlet
n2 - n1
binding energy
“Feshbach” molecules
Transfer of “Feshbach” molecules to
“deeply” bound states
Rb2 Hecker Denschlag et al
Summary and Conclusions on alkali dimers
Full potentials at ground state asymptote “available”
with sufficient accuracy
LiCs, NaRb, NaCs, KRb
Na2 , K2 (Li, Rb, Cs)
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in progress
LiK, KCs, LiRb
Feshbach resonance structure very rich
Binding energies from photoassociation desired
Approximations: atomic hyperfine interaction
neglected second order spin-orbit interaction
Born-Oppenheimer approximation
Electronic structure of excited states very complex
Doorways to cold molecules
with good predictions of transition moments from theory
KRb scattering lengths (units of a0)
LENS
Feshbach
data
isotope
40 / 87
40 / 85
39 / 85
39 / 87
41 / 85
41 / 87
singlet
-111(5)
64.5(6)
26.5(9)
triplet
-215(10)
-28.4(16)
63.0(5)
824(+99/-70)
35.9(7)
106.0(8)
348(10)
14.0(11)
163.7(16)
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this work
singlet
triplet
-111.5
-215.6
65.8
-28.55
33.4
63.9
1868
35.9
103.1
350
7.06
164.4
vmax
40 / 87
39 / 85
39 / 87
97(+/-2)
31(+/-2)
99
98
99
deviations
consistence
LENS: Phys. Rev. A 73, 040702 (2006)
erratum: Phys. Rev. A 74, 039903 (2006)
31
31
31
Coherent excitation scheme to the cold collision regime
25000
ns+np
v'A =100-140
20000
1 +
A u
L3
energy [cm-1]
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15000
fluorescence
Example Na2
vA=15
L2
fluorescence
10000
3 +
a u
L1
ns+ns
5000
0
vX =0
2
vX =29
X  g+
1
3
4
5
6
internuclear distance [Å]
7
8
L1
9
10
Stokes laser
L3
pump laser
L2
molecular beam
fluorescence
fluorescence
Scattering spectroscopy
0
10mK
kinetic energy
Example Na+Na
Comparison with simulation
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Construction of the adiabatic ground state potentials
inner part Ri (s)
Ri (t)
Ro(t,s)
Vs / t ( R)  As / t  Cs / t / R n
V R   -
6000
energy (cm-1)
long range part
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C6 C8
-   Eex
R 6 R8
Eex R   Aex  R   e - Bex R
continuous &
@transition Ri
3000
fit to exp. data:
V(R) = + a1x + a2x2 + a3x3 + ... - D
R-R
x (R,b) = R + bRe
e
0
1
2
4
6
8 10
R(Å)
20
40
60
Spectrum for state a3+
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